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The intermolecular oxypalladation of chiral nonracemic allylic alcohols (S)-1, (R)-1 and (R)-3 in methanol has given chiral nonracemic methyl allyl ethers (S)-2 and (R)-2 with excellent selectivity. The byproduct is formed through the second syn-oxypalladation from the methyl allyl ether, although the rate of this second reaction is much slower than that of allylic alcohol.

Photochemistry of mycolactone A/B and related unsaturated fatty acid esters is reported. On exposure to visible light, mycolactone A/B gave a mixture of four photomycolactones. Pentaenoates and tetraenoates, representing the unsaturated fatty acid portion of mycolactone A/B, were found to show the reactivity profile parallel with that of mycolactone A/B. The structure of the four photomycolactones was elucidated via (1) structure determination of the four photoproducts in the tetraenoate series; (2) their transformation to the photoproducts in the pentaenoate and then mycolactone series. Triplet quenchers did not affect the photochemical transformation, thereby indicating an event at the singlet state. A concerted, photochemically allowed [4πs + 2πa] cycloaddition was suggested to account for the observed result. This study provided the structurally defined and homogeneous material, which allowed demonstration that photomycolactones exhibit significantly reduced cytotoxicity, compared with mycolactone A/B. [ABSTRACT FROM AUTHOR]

The intermolecular oxypalladation of chiral nonracemic allylic alcohols (S)-1, (R).-1, and (R)-3 in methanol gave chiral nonracemic methyl allyl ethers (S)-2 and/or (R)-2 with excellent selectivity. The reaction induced the 1 ,3-chirality transfer to give syn-SN2' product exclusively through syn oxypalladation. On the other hand, the anti-SN2' product was produced in 20-33% in THF, toluene, and CH2CI2 and predominantly in CH3CN. The π-olefin-Pd complexes I and II are proposed as important intermediates to explain the synand anzi-oxypalladation pathways. The byproduct 9 was formed through the second syn-oxypalladation from the methyl allyl ether 2, though the rate of this second reaction was far slower than that of allylic alcohol. [ABSTRACT FROM AUTHOR]

An efficient and general method for 2- and 2,6-substituted piperidine syntheses using PdII-catalyzed 1,3- chirality transfer reaction has been developed. The various N-protected ζ-amino allylic alcohols cyclize in the presence of PdCl2(CH3CN)2 to give substituted piperidines with high stereoselectivities. The syntheses of (S)-(+)- and (R)-(-)-coniine were achieved in 3 steps from the optically pure allylic alcohols (S)-14c and (R)-14c, respectively. Although the rates of reactions were significantly accelerated in CH2Cl2, THF gave the highest stereoselectivity. PdCl2(CH3CN)2 was found to be the best catalyst for this transformation. A plausible reaction pathway involving the formation of the Pd π-complex directed by the chiral secondary allylic alcohol followed by syn-azapalladation, and subsequent syn-elimination of PdCl(OH) is proposed. [ABSTRACT FROM AUTHOR]

An efficient and general method for 2- and 2,6-substituted piperidine syntheses using Pd(II)-catalyzed 1,3-chirality transfer reaction has been developed. The various N-protected zeta-amino allylic alcohols cyclize in the presence of PdCl2(CH3CN)2 to give substituted piperidines with high stereoselectivities. The syntheses of (S)-(+)- and (R)-(-)-coniine were achieved in 3 steps from the optically pure allylic alcohols (S)-14c and (R)-14c, respectively. Although the rates of reactions were significantly accelerated in CH2Cl2, THF gave the highest stereoselectivity. PdCl2(CH3CN)2 was found to be the best catalyst for this transformation. A plausible reaction pathway involving the formation of the Pd pi-complex directed by the chiral secondary allylic alcohol followed by syn-azapalladation, and subsequent syn-elimination of PdCl(OH) is proposed.